Mirror of Raidz for data reliability

[George Kontostanos]

On Tue, May 15, 2012 at 2:55 PM, Marcelo Araujo <araujobsdport at gmail.com> wrote:
> 2012/5/15 Paul Schenkeveld <freebsd at psconsult.nl>
>
>> On Mon, May 14, 2012 at 01:35:51AM +0800, Marcelo Araujo wrote:
>> > Hi All,
>> >
>> > Me and a co-work are working in a new feature for ZFS, we have 2 Machines
>> > and 2 JBOD, every Machine are connected on those JBOD via SAS and we are
>> > trying to make a fail-over server. Currently every each Machine has two
>> SAS
>> > cables, each one connected in both JBOD.
>> >
>> > We have worked last week to figure out, how we could make the data be
>> > always alive in case one JBOD dies, and let me show you my console output
>> > ;):
>> >
>> > controllerA# zpool status -v araujo
>> >   pool: araujo
>> >  state: ONLINE
>> >  scan: resilvered 57K in 0h0m with 0 errors on Sat May 12 14:32:29 2012
>> > config:
>> >
>> >         NAME          STATE     READ WRITE CKSUM
>> >         araujo        ONLINE       0     0     0
>> >           raidz1-0    ONLINE       0     0     0
>> >             mirror-0  ONLINE       0     0     0
>> >               da0     ONLINE       0     0     0
>> >               da3     ONLINE       0     0     0
>> >             mirror-1  ONLINE       0     0     0
>> >               da1     ONLINE       0     0     0
>> >               da4     ONLINE       0     0     0
>> >             mirror-2  ONLINE       0     0     0
>> >               da2     ONLINE       0     0     0
>> >               da5     ONLINE       0     0     0
>> >
>>
>> Maybe a dumb question, how you you create the above setup?  I seem unable
>> to create a raidz consisting of mirrors neither can I attach a second
>> physical drive to an existing one in a raidz of three single drives:
>>
>>  # zpool create tank raidz1 mirror /dev/da0 /dev/da3 mirror /dev/da1
>> /dev/da4 mirror /dev/da2 /dev/da5
>>  invalid vdev specification: raidz1 requires at least 2 devices
>>
>>  # zpool create tank raidz1 /dev/da0 /dev/da1 /dev/da2
>>  # zpool attach tank /dev/da0 /dev/da3
>>  cannot attach /dev/da3 to /dev/da0: can only attach to mirrors and
>> top-level disks
>>
>>  # zpool upgrade
>>  This system is currently running ZFS pool version 28.
>>
>>  All pools are formatted using this version.
>>
>> Kind regards,
>>
>> Paul Schenkeveld
>>
>
> Hey Paul,
>
> Yes, I'm using the latest version with code modification, it might be a new
> feature.
> The currently ZFS doesn't support this kind of set, that was I ask, if
> there is another way that I supposed to don't know and could do the same
> thing.
>
> If it make sense, maybe, I'll put more effort to bring this kind of stuff
> as a new feature. However, it is not so simple that I could made in few
> days as well as have this feature only on FreeBSD, it will make the code
> inconsistent between our ZFS port and Illumos-gate.
>
> But is interesting.
>
> Best Regards,
> --
> Marcelo Araujo
> araujo at FreeBSD.org
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If you have 2 machines then your best bet would be HAST.
If you are worried about data replication you can always use lagg with
2 or more interfaces.

-- 
George Kontostanos
Aicom telecoms ltd
http://www.aisecure.net